Defibrillator system

ABSTRACT

The invention provides a portable defibrillation system ( 2 ), including: a high voltage switch, and current control circuit ( 16 ) connectable to and fed by a power source ( 6 ); a high voltage transformer ( 14 ) fed by the current control circuit; a pair of electrode pads ( 12, 12′ ) connected to the high voltage transformer, and a computer-based controller ( 18 ), operationally connected to the current control circuit, for governing the application of current to the high voltage transformer and, in turn, to the electrodes, wherein the high voltage applied to a patient by means of the electrode pads is directly derived from the power source.

FIELD OF THE INVENTION

The present invention relates to intensive care systems for the earlytreatment of sudden arrhythmias, and more particularly, to such systemswhich are suitable for domestic or outpatient use by non-medicalpersonnel, on a dying patient.

BACKGROUND OF THE INVENTION

Heretofore, sudden cardiac death caused by ventricular fibrillation orcardiac arrest, was the major cause of death among the adult populationin developed countries. Ventricular fibrillation can be halted andnormal heart activity restored, by the electrical defibrillationprocedure, comprising an electric shock applied to the heart. Similarly,heart arrest can be treated by pacing electrical signals, that is, apulse train, at the rate of 60-80 pulses per minute. The defibrillationprocedure is usually effective when applied in intensive care units inhospitals, where a state of fibrillation is easily detected andtreatment is quickly applied. Hospital intensive care units are usuallyequipped with expensive defibrillation equipment, along withprofessional personnel who are able to perform the treatment.

The above considerations also apply to the state of heart arrest and theuse of an external pacemaker device. Thus, while the description of thepresent invention relates to defibrillators, it should be understoodthat it is also meant to include pacemaker systems.

It is of paramount importance that a defibrillation procedure be doneimmediately; otherwise, irreversible, irreparable damage is caused. Thepatient's brain is be damaged within minutes of the start offibrillation, due to a lack of oxygen supply, and all other organs willstop functioning. Early defibrillation restores cardiac function andspontaneous respiration, avoiding anoxic brain damage. In addition,there is a clear linkage between the elapsed time between the beginningof ventricular fibrillation, the beginning of the defibrillationprocedure, and the procedure's success.

The majority of potential fibrillation victims live at home, however,and are not under constant medical supervision. This is even more sowith the modern trend towards treatment of patients at home. Thesepeople cannot be given immediate defibrillation treatment, for severalreasons:

-   1) From the moment that the victim of ventricular fibrillation loses    consciousness, it will take at least from 10-20 minutes until the    mobile care unit reaches him. Therefore, in such cases    defibrillation is usually not successful and irreversible cardiac    damage is caused; if the patient survives, he will remain in coma    with permanent brain damage.-   2) Presently used defibrillation equipment is expensive, costing in    the range of thousands of dollars. The majority of the people cannot    afford to include such equipment as part of their home first aid    kits.-   3) Much of the presently used defibrillation equipment must be    operated by professional, trained medical personnel, who diagnose    the case as fibrillation, find the right equipment, and use it    correctly to apply electric shock at the proper location.    Non-professional people are unfamiliar with such equipment; and    moreover, they tend to panic and be ineffective in an emergency    situation. Therefore, family members and neighbors usually cannot be    relied upon to perform defibrillation treatment.-   4) The defibrillation equipment has to be kept in good operating    condition so that it will be ready for use in an emergency. Hospital    maintenance teams routinely keep all equipment in good condition and    perform required periodical tests and repairs. It is difficult,    however, to keep complex defibrillation equipment in good condition    at home and to do the required testing and repairs.-   5) Defibrillation equipment may be dangerous if misused. High    voltages generated by the equipment can endanger its operators,    children, or other non-professionals. The existing equipment lacks    the safety devices which are required for home use.

SUMMARY OF THE INVENTION

It is therefore an object of the present invention to overcome theabove-mentioned problems and to provide a low-cost, automaticdefibrillation system utilizing available alternating current, fortreating fibrillation and cardiac arrest patients at home.

Thus, the invention provides a portable defibrillation system,comprising a high voltage switch and current control circuit connectableto and fed by a power source; a high voltage transformer fed by saidcurrent control circuit; a pair of electrode pads connected to the highvoltage transformer, and a computer-based controller, operationallyconnected to the current control circuit, for governing the applicationof current to the high voltage transformer and, in turn, to theelectrodes, wherein the high voltage applied to a patient by means ofthe electrode pads is directly derived from the power source.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in connection with certain preferredembodiments with reference to the following illustrative figures so thatit may be more fully understood.

With specific reference now to the figures in detail, it is stressedthat the particulars shown are by way of example and for purposes ofillustrative discussion of the preferred embodiments of the presentinvention only, and are presented in the cause of providing what isbelieved to be the most useful and readily understood description of theprinciples and conceptual aspects of the invention. In this regard, noattempt is made to show structural details of the invention in moredetail than is necessary for a fundamental understanding of theinvention, the description taken with the drawings making apparent tothose skilled in the art how the several forms of the invention may beembodied in practice.

In the drawings:

FIG. 1 is a block diagram of the defibrillation system according to thepresent invention;

FIG. 2 is a circuit diagram of a first embodiment of the invention;

FIG. 3 depicts graphs showing the waveforms produced at different pointsin the circuit of FIG. 2;

FIG. 4 is a circuit diagram of a second embodiment of the invention;

FIG. 5 depicts graphs showing the waveforms produced at different pointsin the circuit of FIG. 4;

FIG. 6 is a circuit diagram of another embodiment of the invention, and

FIG. 7 depicts graphs showing the waveforms produced at different pointsin the circuit of FIG. 6.

DETAILED DESCRIPTION

Referring now to FIG. 1, there is shown a block diagram of an automaticdefibrillation system 2 according to the present invention. System 2 isconnectable, via switch 4, to a common power source 6, e.g., AC mainsoutlet 8 or, alternatively, to a battery-operated DC-to-AC converter 10,for use when mains power is not available.

System 2 includes a pair of electrodes 12, 12′ electrically connectedto, and fed by, a high voltage output transformer 14, e.g., a step-uptransformer, receiving power from source 6 via a high voltage switch andcurrent control circuit 16. The latter is governed by computer-basedcontroller 18. Advantageously, measurement leads 19, 19′ connectelectrodes 12, 12′ to the computer-based controller 18. The system maybe optionally furnished with an audio-visual alarm 20 and an ECG visualoutput manual operation unit 22.

FIG. 2 illustrates a first embodiment of the invention. System 2 isconnectable via switch 4 to the mains power source 6. A step-downtransformer 24 feeds a power supply 26, providing the required DCvoltage to the system. A zero cross detector 28 is connected to thelow-voltage side of transformer 24, and detects the exact timing of thezero crossing of the mains sine wave, to be used as a reference for theoperation of the system. A monostable 30, e.g., a 30 msec monostable, iseither manually triggered by push button 32 or automatically throughleads 34 to a computer (not shown) for analyzing the ECG signals of apatient. The computer is connected to a main gate synchronizer 36, whichsynchronizes between the input signals arriving from the zero crossingdetector 28 and the signals arriving from the monostable 30. The outputfrom main gate synchronizer 36 is fed to a positive half-cycle detector38, for detecting the beginning of a first positive half-cycle of themains occurring in response to manual or automatic triggering.

As a first part of the procedure for controlling the power that will betransferred through the output transformer 14 to the electrodes 12, 12′,circuit 40 enables a time delay of, e.g., 0 to 5 msec, counted from thezero crossing of the sine wave. This delay marks the beginning of thepulse of energy transferred to the patient. The second part of thepower-controlling procedure comprises generating a pulse in generator42, e.g., 1 to 10 msec wide, according to the amount of energy that hasto be transferred to transformer 14 and thence, via electrodes 12, 12′,to the patient.

The high voltage switch and current control 16 can be divided into twocomponents: IGBT control 16′, which transforms the logic levels used inthe other parts of the system to the levels required to trigger the highcurrent IGBT switch 16″. The latter is a high power switch supplying theprimary of high voltage transformer 14 with an adequate waveform, shapedby pulse width generator 42.

Referring now also to FIG. 3, the system's waveforms are shown inalignment, including the mains waveform A, the zero cross output signalB, monostable 30 output signal C, main gate 36 synchronizing signal D,first positive half-cycle signal E, delay signal F, pulse width waveformG at the output of the pulse width generator 42, and the actual highvoltage output waveform H, which is applied to electrodes 12, 12′.

Thus, from the synchronized signal, the zero crossing pulse precedingthe first positive half-cycle is selected and used as a triggeringsignal for the generation of a pulse whose beginning timing and endtiming can be controlled in order to ensure that the required amount ofenergy is transferred to the patient. This pulse is, in turn, used as agating signal to the high current switch applying the mains' power tothe step-up output transformer 14, used to obtain the required highvoltage to be applied to the patient's chest.

FIGS. 4 and 5 depict a modification of the embodiment of FIGS. 2 and 3,in which there is provided a high frequency generator 44 for providing atrain of high frequency (A, FIG. 5), e.g., a 12 to 24 KHz sinusoidalwaveform B, to be used as a power source for the step-up outputtransformer 14. After passing through a wave shaper 46, the pulses areshaped as shown at H. The high voltage output applied to the patient isthus shown as I of FIG. 5. The wave shaper 46 enables the application ofconsecutive pulses shaped according to the requirements within limits ofless than 200 ms delay, in contrast with known systems based oncapacitor discharge where it takes several seconds before a seconddischarge is possible.

Furthermore, the wave shaper enables the application of pulses shapedaccording to any requirements, within limits of the sine wave, havingvariable peak outputs and starting and stopping at will, creating a monoor biphasic waveform, or continuous wave composed of two or moresegments, thereby enabling the delivery of the exact amount of energyrequired.

A further embodiment is shown in FIGS. 6 and 7. Accordingly, anexponential amplitude controller 48 is connected in circuit between themains and the output transformer 14. The controller 48 is used tocontrol the amplitude (A, FIG. 7) of the sinusoidal waveform obtained bythe mains (B, FIG. 7), resulting in a progressively reduced high voltagewaveform C. Amplitude decrease is calculated by the system in such a waythat the accumulated energy transferred to the patient reaches therequired value determined by the patient's condition and other, per seknown, considerations.

It will be evident to those skilled in the art that the invention is notlimited to the details of the foregoing illustrated embodiments and thatthe present invention may be embodied in other specific forms withoutdeparting from the spirit or essential attributes thereof. The presentembodiments are therefore to be considered in all respects asillustrative and not restrictive, the scope of the invention beingindicated by the appended claims rather than by the foregoingdescription, and all changes which come within the meaning and range ofequivalency of the claims are therefore intended to be embraced therein.

1. A portable defibrillation system, comprising: a high voltage switchand current control circuit connectable to and fed by an AC powersource; a high voltage transformer fed by said current control circuit;a pair of electrode pads connected to said high voltage transformer, anda computer-based controller, operationally connected to said currentcontrol circuit, for governing the application of current to said highvoltage transformer and, in turn, to said electrodes; wherein the highvoltage applied to a patient by means of said electrode pads is directlyderived from said AC power source.
 2. The portable defibrillation systemas claimed in claim 1, further comprising measurement leads connectingsaid electrodes with said computer-based controller.
 3. The portabledefibrillation system as claimed in claim 1, wherein said AC powersource is selected from the group consisting of a mains AC power outletand a battery-operated DC to AC converter.
 4. The portabledefibrillation system as claimed in claim 1, further comprising anaudio-visual alarm connected to said computer-based controller.
 5. Theportable defibrillation system as claimed in claim 1, further comprisingan ECG visual output manual operation connected to said computer.
 6. Theportable defibrillation system as claimed in claim 1, wherein saidcomputer-based controller is connected to said power source via a zerocrossing detector for establishing a system operation reference.
 7. Theportable defibrillation system as claimed in claim 6, further comprisinga main gate synchronizer connected to said zero crossing detector and apatient's ECG signal.
 8. The portable defibrillation system as claimedin claim 1, further comprising a wave shaper for shaping voltage pulsesproduced by said high voltage transformer.
 9. The portabledefibrillation system as claimed in claim 8, wherein said wave shaper iscapable of application of pulses with a variable peak output voltagefacilitating delivery of an exact amount of energy required.
 10. Theportable defibrillation system as claimed in claim 1, further comprisingan exponential amplitude controller connected in circuit between saidpower source and said high voltage transformer.